I wouldn't start with procedural programming. I think
a spreadsheet is a much better starting point.

It is satifying to work with a spreadsheet because
it does such a nice job of formatting the work.
This gives the student a feeling of accomplishment.

Computing some sort of average having
to do with sports would be interesting for many 8 year
olds. This helps cross a language barrier, since
sports have a well-defined vocabulary.

Another good exercise is to have them build a
computer. I was able to get 30 students to make
their own slide rules in twenty minutes. I gave
them a quick demo of an adder by using two rulers.
Then I gave each of them a log table (with the
numbers expressed as lengths) and a ruler, and
they made slide rules out of paper.

Another example was a prime number generator.
One group wrote the sequence of numbers on small
slips of paper and handed it off to a chain of
others who implemented the sieve of Eratosthenes.
It was pandemonium, and fun to watch!
(Hint - the bottleneck is at the divide-by-7 table).